ENLARGLNG AND SEDUCING.
amateur will have frequently to make an enlargement or reduction of a picture or photograph, or copy exact size; and to enlarge or reduce from a negative. Reduction from a picture can be done in an ordinary camera, and full-size copies can also be made, if they are not to be larger than the largest size of the plate used with the camera, by attaching a cone to the front, and placing the lens at the extreme end of the cone. The cut above shows how this is arranged.
A different arrangement is required for making enlargements, and we therefore give an illustration of an enlarging, copying and reducing camera.
The entire length of this is about five feet, and it is suitable for making copies either full size, or larger or smaller; for making positives direct from negatives in either size; for making nega tives direct from transparencies or positives; and for making lantern slides direct from large negatives. The cut shows the lens mounted on the central frame, in position for making a re duction or lantern slide, or an enlargement, the negative being placed in one of the kits in the front. with the film side towards the lens. Double sets of kits for all the ordinary sizes of plates usually accompany these cameras, for use in the plate-holders and the front; also a table, showing the location of the lens, with re spect to the front and ground-glass, for different degrees of en largement and reduction, for lenses with a focus of from two to nine inches. In enlarging or reducing from a negative, the light enters through the negative, and the camera should face the open sky. If trees or buildings intervene, the camera should be placed near the window, with a white board or mirror on the outside, inclined upwards at an angle of forty-five degrees, to reflect the light into the camera, avoiding sunlight. The time of exposure
will depend upon the amount of light, the quality of the negative, the sensitiveness of the plate or paper, and the degree of enlarge ment. The larger the copy required, the longer in proportion must be the exposure. If an exposure of two minutes is correct for enlarging a 4 x 5 to an 8 x 10. it will require eight minutes to enlarge to 16 x 20, etc.
The correct exposure must largely be a matter of experiment. We have found the time for enlarging on bromide paper on a bright day to double size, (note that 8 x10 is four times the size of 4 x 5), varies with different negatives from about one and a half to two and a half minutes , enlarging from a 4 x 5 transpar ency to an 8 x10 Carbutt 16 plate to take from forty to ninety seconds, with an f32 stop; to make lantern slides on a bright day to vary from two and a half to fifteen minutes, the latter extreme being from a very intense negative.* In experiments, for the purpose of determining the correct time, it is not necessary to waste large plates or large sheets of bromide paper, as a small piece of the paper or a quarter plate will answer as well, to receive simply- a portion of the enlargement.
In enlarging or reducing from a negative or transparency use the smallest stop; in enlarging from a picture or photograph use a medium size stop. In the latter case, if a small stop were used it would have the effect of showing too plainly the imper fections or grain of the paper.